/*
* Find the next DST transition time at or after the given time
*
* *timep is the input value, the other parameters are output values.
*
* When the function result is 1, *boundary is set to the time_t
* representation of the next DST transition time at or after *timep,
* *before_gmtoff and *before_isdst are set to the GMT offset and isdst
* state prevailing just before that boundary, and *after_gmtoff and
* *after_isdst are set to the state prevailing just after that boundary.
*
* When the function result is 0, there is no known DST transition at or
* after *timep, but *before_gmtoff and *before_isdst indicate the GMT
* offset and isdst state prevailing at *timep. (This would occur in
* DST-less time zones, for example.)
*
* A function result of -1 indicates failure (this case does not actually
* occur in our current implementation).
*/
int
pg_next_dst_boundary(const pg_time_t *timep,
long int *before_gmtoff,
int *before_isdst,
pg_time_t *boundary,
long int *after_gmtoff,
int *after_isdst,
const pg_tz *tz)
{
const struct state *sp;
const struct ttinfo *ttisp;
int i;
int j;
const pg_time_t t = *timep;
sp = &tz->state;
if (sp->timecnt == 0)
{
/* non-DST zone, use lowest-numbered standard type */
i = 0;
while (sp->ttis[i].tt_isdst)
if (++i >= sp->typecnt)
{
i = 0;
break;
}
ttisp = &sp->ttis[i];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
return 0;
}
if ((sp->goback && t < sp->ats[0]) ||
(sp->goahead && t > sp->ats[sp->timecnt - 1]))
{
/* For values outside the transition table, extrapolate */
pg_time_t newt = t;
pg_time_t seconds;
pg_time_t tcycles;
int64 icycles;
int result;
if (t < sp->ats[0])
seconds = sp->ats[0] - t;
else
seconds = t - sp->ats[sp->timecnt - 1];
--seconds;
tcycles = seconds / YEARSPERREPEAT / AVGSECSPERYEAR;
++tcycles;
icycles = tcycles;
if (tcycles - icycles >= 1 || icycles - tcycles >= 1)
return -1;
seconds = icycles;
seconds *= YEARSPERREPEAT;
seconds *= AVGSECSPERYEAR;
if (t < sp->ats[0])
newt += seconds;
else
newt -= seconds;
if (newt < sp->ats[0] ||
newt > sp->ats[sp->timecnt - 1])
return -1; /* "cannot happen" */
result = pg_next_dst_boundary(&newt, before_gmtoff,
before_isdst,
boundary,
after_gmtoff,
after_isdst,
tz);
if (t < sp->ats[0])
*boundary -= seconds;
else
*boundary += seconds;
return result;
}
if (t > sp->ats[sp->timecnt - 1])
{
/* No known transition >= t, so use last known segment's type */
i = sp->types[sp->timecnt - 1];
ttisp = &sp->ttis[i];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
return 0;
}
if (t <= sp->ats[0])
{
/* For "before", use lowest-numbered standard type */
i = 0;
while (sp->ttis[i].tt_isdst)
if (++i >= sp->typecnt)
{
i = 0;
break;
}
ttisp = &sp->ttis[i];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
*boundary = sp->ats[0];
/* And for "after", use the first segment's type */
i = sp->types[0];
ttisp = &sp->ttis[i];
*after_gmtoff = ttisp->tt_gmtoff;
*after_isdst = ttisp->tt_isdst;
return 1;
}
/* Else search to find the containing segment */
{
int lo = 1;
int hi = sp->timecnt;
while (lo < hi)
{
int mid = (lo + hi) >> 1;
if (t < sp->ats[mid])
hi = mid;
else
lo = mid + 1;
}
i = lo;
}
j = sp->types[i - 1];
ttisp = &sp->ttis[j];
*before_gmtoff = ttisp->tt_gmtoff;
*before_isdst = ttisp->tt_isdst;
*boundary = sp->ats[i];
j = sp->types[i];
ttisp = &sp->ttis[j];
*after_gmtoff = ttisp->tt_gmtoff;
*after_isdst = ttisp->tt_isdst;
return 1;
}
/* DetermineTimeZoneOffset()
*
* Given a struct pg_tm in which tm_year, tm_mon, tm_mday, tm_hour, tm_min, and
* tm_sec fields are set, attempt to determine the applicable time zone
* (ie, regular or daylight-savings time) at that time. Set the struct pg_tm's
* tm_isdst field accordingly, and return the actual timezone offset.
*
* Note: it might seem that we should use mktime() for this, but bitter
* experience teaches otherwise. This code is much faster than most versions
* of mktime(), anyway.
*/
int
DetermineTimeZoneOffset(struct tm * tm, pg_tz *tzp)
{
int date,
sec;
pg_time_t day,
mytime,
prevtime,
boundary,
beforetime,
aftertime;
long int before_gmtoff,
after_gmtoff;
int before_isdst,
after_isdst;
int res;
if (tzp == session_timezone && HasCTZSet)
{
tm->tm_isdst = 0; /* for lack of a better idea */
return CTimeZone;
}
/*
* First, generate the pg_time_t value corresponding to the given
* y/m/d/h/m/s taken as GMT time. If this overflows, punt and decide the
* timezone is GMT. (We only need to worry about overflow on machines
* where pg_time_t is 32 bits.)
*/
if (!IS_VALID_JULIAN(tm->tm_year, tm->tm_mon, tm->tm_mday))
goto overflow;
date = date2j(tm->tm_year, tm->tm_mon, tm->tm_mday) - UNIX_EPOCH_JDATE;
day = ((pg_time_t) date) * SECS_PER_DAY;
if (day / SECS_PER_DAY != date)
goto overflow;
sec = tm->tm_sec + (tm->tm_min + tm->tm_hour * MINS_PER_HOUR) * SECS_PER_MINUTE;
mytime = day + sec;
/* since sec >= 0, overflow could only be from +day to -mytime */
if (mytime < 0 && day > 0)
goto overflow;
/*
* Find the DST time boundary just before or following the target time. We
* assume that all zones have GMT offsets less than 24 hours, and that DST
* boundaries can't be closer together than 48 hours, so backing up 24
* hours and finding the "next" boundary will work.
*/
prevtime = mytime - SECS_PER_DAY;
if (mytime < 0 && prevtime > 0)
goto overflow;
res = pg_next_dst_boundary(&prevtime,
&before_gmtoff, &before_isdst,
&boundary,
&after_gmtoff, &after_isdst,
tzp);
if (res < 0)
goto overflow; /* failure? */
if (res == 0)
{
/* Non-DST zone, life is simple */
tm->tm_isdst = before_isdst;
return -(int) before_gmtoff;
}
/*
* Form the candidate pg_time_t values with local-time adjustment
*/
beforetime = mytime - before_gmtoff;
if ((before_gmtoff > 0 &&
mytime < 0 && beforetime > 0) ||
(before_gmtoff <= 0 &&
mytime > 0 && beforetime < 0))
goto overflow;
aftertime = mytime - after_gmtoff;
if ((after_gmtoff > 0 &&
mytime < 0 && aftertime > 0) ||
(after_gmtoff <= 0 &&
mytime > 0 && aftertime < 0))
goto overflow;
/*
* If both before or both after the boundary time, we know what to do
*/
if (beforetime <= boundary && aftertime < boundary)
{
tm->tm_isdst = before_isdst;
return -(int) before_gmtoff;
}
if (beforetime > boundary && aftertime >= boundary)
{
tm->tm_isdst = after_isdst;
return -(int) after_gmtoff;
}
/*
* It's an invalid or ambiguous time due to timezone transition. Prefer
* the standard-time interpretation.
*/
if (after_isdst == 0)
{
tm->tm_isdst = after_isdst;
return -(int) after_gmtoff;
}
tm->tm_isdst = before_isdst;
return -(int) before_gmtoff;
overflow:
/* Given date is out of range, so assume UTC */
tm->tm_isdst = 0;
return 0;
}
